1. Field of the Invention
This invention is in the field of producing agglomerates such as ore pellets from filter cakes produced in a solidsliquid filter.
2. Description of the Prior Art
There are available methods and apparatus for the agglomeration of fine grained iron ore such as the ores present in sludge, from which the agglomeration takes place during and with the aid of a filtering-dehydration step. The agglomerates thus formed are conveyed to a calcining operation. An example of this type disclosure would be found in German Pat. No. 1,920,219.
In the known method, the steps of filtering-hydration and the agglomeration are carried out simultaneously. With this type of method, relatively dense agglomerates can be produced from the ore sludge, the agglomerates being adapted to a subsequent drying and sintering operation.
Another apparatus consists of a rotatable filter drum which is partially immersed in the ore sludge, with a filter cake depositing on the surface of the filtered drum. An endless slotted band is provided about the filter cake in the immersion area of the filter drum that is moved together with the filter drum. In the intermediate spaces, the filter cake is deposited on the filter drum surface in the form of individual agglomerates. The endless slotted band with the encased agglomerates is then conveyed to a device which releases the agglomerates from the slotted band openings. In this type of apparatus, the sludge storage for feeding the filtered side is disposed on the lower side of the filter drum and is immersed therein.
This type of apparatus operates without significant difficulty and supplies relatively dense agglomerates in satisfactory quality and quantity. Both the quality and the quantity of the agglomerates are improved as the weight of the sludge or the sludge density increases. The method becomes more economical with a wider spectrum of grain sizes. To a certain degree, a relatively widely dispersed grain spectrum is beneficial in the subsequent process steps of drying and sintering, as well as utilization of the agglomerates as feed material for a blast furnace, or as material to be used in a direct reduction process, for example, in a rotary kiln.
With increasing sludge weights and individual grain sizes, however, with a sludge storage chamber disposed below the filter, a certain amount of undesirable sedimentation of the solid particles in the sludge storage occurs, requiring stoppage of the equipment. This condition limits the efficient carrying out of the process since the strong turbulence in the sludge bath required for making a uniform dispersion disturbs or even prevents the formation of the filter cake in the multi-cavity slotted band. There is also an additional disadvantage in that the fine parts of the sludge arrive first at the filter medium to impair its permeability and accordingly impair the filtering function.